Bukkit

Here is the basics:

[CPU] = Processor usage
[MEM] = Memory usage
[IO] = Storage write/read usage
[FPS] = Client side frames per second
[N/A] = No impact on resource usage

If the + or - symbol comes after, like this [CPU+], it means that it will increase that resource usage. If the symbol comes before, like [-CPU], it means that it will decrease that resource usage.

Thats is not exactly how much the cpu usage will increase, is just to give you an idea of how much.

[CPU---]    = +0.5%\\
[CPU--]     = +2.0%\\
[CPU-]      = +3.0%\\
[CPU+-]    = +3.5%\\
[CPU+]     = +4.0%\\
[CPU++]   = +6.0%\\
[CPU+++] = +10.%

[---CPU]    = -10.%\\
[--CPU]     = -6.0%\\
[-CPU]      = -4.0%\\
And so on...

EngineOptions:\\
  EngineMode: 0 = [CPU-], 1 = [CPU+], 2 = [CPU+++], 3 = [CPU+-], 4 = [CPU++]\\
  NetherEngine: 0 = [CPU-], 1 = [CPU+], 2 = [CPU+++], 3 = [CPU+-], 4 = [CPU++]\\
  HideOnDark: if true [CPU---]\\
  FakeCaves:\\
    Enabled: if true on Engine Mode 0 or 1 [CPU++], on Engine Mode 2, 3 or 4 [CPU---]\\
    Intensity: higher values on server side: [CPU-], client side [--FPS]\\
  HideChests: if true on Engine Mode 0 or 1 [CPU++], on Engine Mode 2, 3 or 4 [CPU---]

Cache:\\
  Enabled: if true [---CPU], [IO++], [MEM+]\\
  MemoryCache: higher values [--CPU], [MEM++]\\
  FileCallGC: lower values [CPU+], higher values [-CPU], [MEM+]\\
  SizeLimit: [N/A]\\
  Compression: higher values [CPU+++], lower values [CPU--], 0 = [CPU---].

BlockUpdate:\\
  UpdateRadius: higher values [CPU-]\\
  LightUpdate:\\
    Enabled: if true [CPU-]\\
    LightRadius: higher values [CPU+]\\
    LightSource: [N/A]\\
  UpdateOn:\\
    BlockExplosion: if true [CPU++]\\
    BlockPiston: if true [CPU++]\\
    BlockPhysics: if true [CPU+]\\
  Proximity:\\
    Enabled: if tue [CPU+++]\\
    Radius: higher values [CPU+++]\\
    Distance: higher values [-CPU]

RandomBlocks:\\
  World: [N/A]\\
  Nether: [N/A]\\
  \\
HiddenBlocks:\\
  World: [N/A]\\
  Nether: [N/A]

Worlds:\\
  Disabled:\\
    - More disabled worlds [---CPU]\\